Navy Asbestos Medical Surveillance Program (1984-1990): linear regression analysis for effect of asbestos exposure on pulmonary function testing

Our plain-English summary of Navy Asbestos Medical Surveillance Program (1984-1990): linear regression analysis for effect of asbestos exposure on pulmonary function testing, by B.K. Bohnker, L.S. Betts, D.M. Sack, et al (Military Medicine, 2004).

The study

• Authors: B.K. Bohnker, L.S. Betts, D.M. Sack, N.A. Craft
• Journal: Military Medicine
• Published: 2004;169(8):613-9
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

This study examined records from the Navy Asbestos Medical Surveillance Program for 1984 through 1990 for Caucasian men (N = 129,598) using a population-based, cross-sectional, linear regression model. Continuous dependent variables were forced expiratory volume in 1 s and forced vital capacity (FVC), and continuous independent variables were age, height, weight, and tobacco use. A mid-period estimate of asbestos exposure was used because those values were reported as categorical variables. With asbestos exposure, forced expiratory volume in 1 s changed -3.2 cm3/year (t = -8.6, p = 0.000), and forced vital capacity changed -5.1 cm3/year (t = -11.8, p = 0.00). Those with more than 5 years of asbestos exposure demonstrated impairment over those with less exposure, and those with more than 15 years of exposure demonstrated even more impairment. These findings support the association of pulmonary function impairment with asbestos exposure for workers studied during this period.

In plain English

This cross-sectional study used linear regression on U.S. Navy Asbestos Medical Surveillance Program records from 1984 through 1990. It covered Caucasian men aged 30 to 60, with 129,595 records according to the article text. Exposure was the self-reported number of years of asbestos exposure, recorded in categories. Fiber types were not named. Two lung function measures, FEV1 and FVC, were adjusted for age, height, weight, years of smoking and examination year. Each estimated year of exposure was associated with 3.2 cm3 lower FEV1 and 5.1 cm3 lower FVC. Men with 1 to 5 years of exposure did not differ significantly from those with less than 1 year. Men with 5 to 15 years had FEV1 30.2 cm3 and FVC 45.5 cm3 lower than those with less than 5 years. Men with more than 15 years had FEV1 58.7 cm3 and FVC 89.5 cm3 lower than those with less than 15 years. A year of smoking had about three to four times the effect on FEV1 of a year of asbestos exposure. The authors concluded that the findings support an association between asbestos exposure and impaired lung function. They noted that self-reported exposure could introduce bias, and that the design could not assess cancer or deaths.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Population-based, cross-sectional linear regression analysis of medical surveillance records
• Who was studied: Caucasian men in the U.S. Navy Asbestos Medical Surveillance Program, examined 1984 through 1990. Records were limited to ages 30 to 60, and records with implausible smoking, height or weight values were excluded. The text gives 129,595 records; the abstract gives 129,598.
• Exposure: Self-reported duration of asbestos exposure, in categories: none, less than 1 year, 1 to 5 years, 5 to 15 years, more than 15 years. The first two categories were combined. For the main model, the authors used mid-period values of 0, 3, 10 and 20 years. Fiber types and specific products were not named.
• Main results:
  • In the model using mid-period estimates, each year of asbestos exposure was associated with significant impairment: 3.2 cm3 per year for FEV1 and 5.1 cm3 per year for FVC (p reported as 0.000).
  • Men with 1 to 5 years of exposure showed no significant difference from those with less than 1 year. Table II gives p of 0.303 for FEV1 and 0.658 for FVC.
  • Men with 5 to 15 years of exposure showed significant impairment compared with those with less than 5 years: FEV1 30.2 cm3 and FVC 45.5 cm3.
  • Men with more than 15 years of exposure showed significant impairment compared with those with less than 15 years: FEV1 58.7 cm3 and FVC 89.5 cm3.
  • Smoking was associated with impairment of about 12 cm3 per year for FEV1 and 9 cm3 per year for FVC. One year of smoking had about three to four times the adverse effect on FEV1 of one year of asbestos exposure.
  • An interaction between asbestos exposure and smoking was found only in the comparison of 5 to 15 years with less than 5 years of exposure.
• The authors' conclusion: The authors concluded that the findings support an association between asbestos exposure and impaired lung function in the workers studied in this period. They found a statistically significant reduction for more than 5 years of exposure and further impairment for more than 15 years.
• Limitations the authors state:
  • Accurate exposure data were not available. Self-reported years of exposure were used instead, which could introduce several kinds of bias.
  • The design cannot assess asbestos-related deaths or cancers such as malignant mesothelioma or lung cancer.
  • Results may differ in populations with more or less workplace exposure, or with more or less effective respiratory protection.
  • Records from 1980 to 1983 were left out because of unresolved uncertainty about how smoking was coded.

Topics

The National Library of Medicine indexes this study under subjects our site covers: The Navy.

Medical terms in this study, explained in our Lexicon: Asbestos Exposure.

Related studies

• Navy Asbestos Medical Surveillance Program (1991-1999): linear regression analysis for the effect of asbestos exposure on pulmonary function testing — B.K. Bohnker, L.S. Betts, et al. (2004)
• Variability in interpretation among B-readers in the U.S. Navy Asbestos Medical Surveillance Program — J.G. Muller, J.M. Lieske, et al. (2008)
• Navy Asbestos Medical Surveillance Program 1990-1999: demographic features and trends in abnormal radiographic findings — D.M. Dell, B.K. Bohnker, et al. (2006)
• Trends in pleural radiographic findings in the Navy Asbestos Medical Surveillance Program (1990-1999) — J.G. Muller, B.K. Bohnker, et al. (2005)
• Changes in B-readings over time in the United States Navy Asbestos Medical Surveillance Program — J.G. Muller, W.G. Rudolph, et al. (2007)
• Evaluation of the national health surveillance program of workers previously exposed to asbestos in Spain (2008) — M.G. Gómez, R. Castañeda, et al. (2012)

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